1. Field of the Invention
The present invention relates to systems and methods for inspecting panels, and particularly to a system and method for inspecting liquid crystal display (LCD) panels.
2. Related Art of the Invention
With the merits of small volume and light weight, LCDs have the edge over conventional cathode ray tube (CRT) displays in the market for portable display devices and compact application displays. LCDs are being produced in increasingly larger volumes to meet the increasing demand. A typical LCD has a liquid crystal material sandwiched between an active plate and a ground plate. Polarizers, colorizing filters and spacers may also be included between the plates. During fabrication, many active panels may be formed on a single glass plate. In each area of the glass plate that is to form an active panel, pixel areas, drive lines, gate lines and drive elements are formed. Typically, thin-film transistors are used for the drive elements.
Because of the relative complexity of the active plate in comparison to the ground plate, most LCD defects can be traced to some form of defect in the active plate. When a defective active plate is detected, repair of the active plate or discarding of the entire LCD are both costly. Thus various tests have been developed for inspecting active plates alone, so that defective active plates can be identified and repaired or discarded at a relatively early stage of the fabrication process. A typical testing method is to connect an array tester to the signal lines and gate lines on the active plate. The array tester sequentially transmits predetermined signals to the signal lines or gate lines, then sequentially receives and analyzes the signals fed back by the signal lines or gate lines in order to locate the defective pixels. The array tester uses probe tips to contact the outer pin of each signal or gate line and transmit the predetermined signals to the signal or gate line. The signals fed back from the signal or gate line are then analyzed as current-voltage (IV) curves using components such as integrators. If any IV curve does not match a predefined standard, the existence of one or more defective pixels is determined. The defective pixels are subsequently identified using an apparatus such as an electron microscope.
However, the testing method described above has some limitations. To carry out the test, the probe tips must precisely contact the outer pin of the signal or gate line. When the active plate has a high resolution, the outer pins are densely arrayed. The apparatus controlling the probe tips to touch the outer pins must be highly precise, and the testing process must be meticulous and laborious. Furthermore, the higher pixel count in a larger LCD requires more testing time. Testing times can have a major effect on manufacturing costs. Good quality control includes short testing times with efficient testing, and can considerably improve yield. Accordingly, there is a need for a simple and convenient system and method for inspecting an LCD which can overcome the above-mentioned problems.